Transferring from Sony DCR SX43 to iMac

I bought this little handycam which has an SD card and came with a USB wire. When I tried to import video into iMovie via the USB, nothing appeared to happen. I tried opening it in Quicktime as well - nada.
My son was able to edit a short movie on a friend's PC which has an SD slot. But I'd hate to think this handycam won't let me edit stuff on my Mac.

I'm not a techy kind of person, but I have a Firewire - can I do a USB to firewire connection somehow and would that help? Will I need to buy an external hard drive?

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